8 AMERICAN BLACK FLIES OR BUFFALO GNATS. 



observations by Jennings and King the females .select a twig, leaf, 

 or blade of grass which is suitable, and approaching the margin of 

 same nearest the water commence ovipositing thereon. The number 

 of eggs deposited is very large, and generally several females ovi- 

 posit on the same leaf, the combined weight of the eggs serving to 

 submerge the leaf or blade of grass and provide the necessary con- 

 ditions for the emergence of the larvae. It has been placed on record 

 that the species which oviposit on rocks have the faculty of entering 

 the water to oviposit on the submerged rock surface. The egg 

 masses on rocks are of very considerable extent and must amount 

 to thousands in number. When first deposited they are covered with 

 a peculiar slimy coating and being pale yellowish in color are very 

 conspicuous, but later on they become darkened and whether on 

 leaves or rocks are not so noticeable. It has been stated by Horvath ^ 

 that the female lays from 5,000 to 10,000 eggs. This is undoubtedly 

 an exaggeration, and the estimate was probably arrived at by con- 

 sidering the accumulated mass deposited by a number of females as 

 being the deposit of only one. The eggs are elongate-oval and are 

 very closely packed together on whatever surface they may be 

 deposited. The egg stage occupies about a week, but is affected by 

 weather conditions and also by the date of deposition. 



LARVA. 



The larvae are cylindrical in shape, attenuated in the middle, and 

 thickened at each end, most distinctly on the posterior third. In 

 length they vary from about 8 to 15 mm. and possess, besides the 

 head, 12 segments. They vary considerably in color, being almost 

 entirely black in p'tctlpes and pale yellowish-white, with slightly 

 darker cross-bands on the segments, in venustiim. The chief charac- 

 ters of use in distinguishing the species are found in the mouthparts. 



The head (PI. VI, fig. 1) is chitinized and slightly flattened. On 

 each side there are, in all the species which I have examined, two 

 irregularly shaped, black, approximated eye-like spots. On the 

 dorsal surface, well forward and near to the bases of tlie fans, are 

 situated the three-jointed antenna? (see PI. VI, fig. 3). The fans 

 (PL III, fig. 5) are composed of a large number of rays (PL VI, 

 fig. 7) which vary in number, and generally in structure, in the 

 different species. The function of these fans seems to be that of guid- 

 ing food into the mouth cavity, moving on an articulated stalk and 

 meeting, when brought forward closed, over the mouth opening. 

 The mandibles, which in most cases furnish characters in their denta- 

 tion for differentiating the species (PL III, figs. 1, 2), are situated 

 lower on the head than the fans, and move so as to close pincers- 



^ " Le moucheron de Columbatch." Rovart. Lapok., 1 Band, pp. 195-204. 



